i'm just about ready to take the dSLR plunge, having grown weary of the consistantly noisy exposures i get from my digital compact p&s. i favor night photography--longer exposures (30 seconds +), typically shooting wide angle, low ISO. ideally, i'd like a camera that could yield 20x30 prints without exhibiting visible digital noise from a typical viewing distance.

unable to draw a satisfactory conclusion from online reviews, as most entry-level dSLRs are rated favorably (bang-for-yr-buck factor). i don't own any lenses yet, know that i favor nikon bodies from an ergonomics standpoint, but given that i'll be using a tripod most of the time, ergonomics aren't the be-all, end-all.

the big question: can i expect to see any significant difference in noise/image quality on long, low ISO exposures between the various entry-
mid-level dSLRs? budget is in the $2000 range, so i've checked out the 20D, as well as the nikon range up to D200. i understand resolution differences come into play with larger prints, but ultimately if lower ISO noise levels are comparable across the board, i'd just as soon get a cheaper body and spend the difference on lenses. or food.